Electric fuse



Patented May 2, 1933 UNITED STATES FTENT OFFICE AUGUSTUS JESSE BOWIE, OF SAN FRANCTSCO, CALIFORNIA ELECTRC FUSE This invention relates to improvements in electric fuses and has particular reference to unfilled high tension fuses, although the same .q principle will apply to fuse tubes which are lled with insulating powder.

A usual type of unfilled fuse consists of a fuse tube with end terminal connections in the form of ferrules, the top connection being y `permanently closed, and the fuse when it blows being expelled from the lower end.

The lower ferrule which is placed ontlie outside of the tube instead of being at the end of the tube is located a short distance back Y A lfrom the end, the tube protruding' beyond the end of the ferrule. The fuse wire is taken fromthe top ferrule thru the tube to the lower end and back up the fuse tube to the bottom ferrule to ywhich it is attached by a screw.

This fuse, as commonly used, has a weakened section near the top end to insure its blowing at this point. This blowing of the fuse will thenveither melt olf or expel the fuse wire from the tube, the heat generated by the arc being ldepended on to accomplish this result.

' Fuses of this nature are subject to two drawbacks: First, when blowing with moderate overload the generated heat may be in sufficient to expel the fuse thoroughly from HMthe tube resulting in the destruction of the tube, and second, if the fuse wire is expelled it is still connected with the lower ferrule and may then dangle downward, a potential menace to anything near by as it may still be alive. In order to be expelled and with- 'drawn from its connection with the lower ferrule, it must be driven out with great force. Thus fuses of this nature which may operate under short circuit will fail under -moderate overload.

40 An important feature in the performance of this type of fuse is the return of the fuse wire up the tube which constitutes a barrier and prevents there-establishment of the ,arc which might occur if the ferrule were 15in a direct line with the blowing of the fuse.

Serial No. 373,392.

It is the object of my invention to overcome the two drawbacks above mentioned. This I accomplish by the closure of the lower part of the fuse tube, preferably by a metal cap inserted in the inner side of the lower ferrule and electrically connected therewith. It will take considerable pressure, which may be regulated however as desired, to expel this cap from the fuse.

One feature of this fuse then is to allow the building up of sufficient pressure so that when the fuse `is expelled from the tube it will be driven out with suflicient violence to extinguish the arc, thus avoiding the diiii culty of the fuse blowing with insuflicient 6l.)

energy behind it to cut olf the ensuing arc.

The second feature of this fuse is to provide means of positively freeing the fuse from the lower ferrule, which is obtained by the positive blow-out and ejection of both the fuse and of its contact cap at the bottom ofthe fuse, thus preventing the dangling down of the fuse wire which might otherwise obvi ate the advantages of the return circuit from the inside of the fuse back to the lower ferrule. This return bend of the fuse is useful in extinguishing the arc.

Figure l shows a. longitudinal cross section of the fuse. Figure 2 shows a half top end view of the fuse. Figure 34 shows a lower end view of the fuse. Figure 4 shows the end of a longitudinal cross-section of the fuse, using an insulating end extension tube.

l is an insulatng fuse tube on which is mounted top ferrule 2. 3 is a metal ring 80 contacting with the top ferrule and 4 is a plug which closes the top of the fuse tube to the atmosphere. 5 is a-contact piece in the top ferrule with attachment screw 6. The fuse is attached by this screw 6 to piece 5 which in turn is clamped by the end cap 4 to ring 8, connecting this to the top ferrule 2. 7 is a fuse whichis single at the top end and is doubled the rest A`of `the way down the tube and is connected to cap 8 9G by screw 9, threaded into piece 13 which serves as a nut. 10 is the lower ferrule, 11 is a ca for closure of the lower end of the fuse. (Bjap 11 fits in an inner recess in ferrule 10 and is secured thereto by its own spring, 11 being made preferably of light materlal. By proper design the pressure of the blow-out of cap 11 may be changed to suit the requirements. Cap 8 is made preferably of light material so that the outer walls thereof will spring out and contact with piece 11. Pieces 8 and 11 are made of metal. 12 is an inner insulating lining of the fuse tube to protect against burning.

In placing the fuse in position it is first connected to cap 8 and then taken thru the tube and connected by screw 6 to piece 5. The closure cap 11 is pressed in place contacting both with 8 and 10 and serving as a medlum of carrying the current from the fuse to the end ferrule. When the fuse blows it will melt at its upper part and will not expel piece 11 until it has generated suiiicient pressure to force it out of ferrule 10. When this has taken place a suiliciently high pressure will have been built up in the tube to expel pieces 8 and 11 with considerable force and at the same time make a positive blow-out of the fuse. While the fuse is shown with tube 1 projecting beyond the outer end of ferrule 10, it is understood any corresponding arrangement may be used, as for example, an extension tube may be inserted in the end of the fuse to accomplish the same result, the principle involved bein the insertion of insulating material whic makes a change in the direction of the fuse thru the tube to its connection with the ferrule 10, and rovides an insulating barrier between the errule 10 and the interior of the adjacent tube end.

In Figure 4, 14 shows an outer insulating tube end, and 15 an inner insulating tube end, which are inserted in the end of the fer-rule 10 instead of having the tube mate rial roject through this ferrule as in Figure 1. therwise the construction is similar to that shown in Figure 1, except that the cap 11 fits over the outer end of ferrule 10 instead of being inserted in the inner part thereof.

What I claim is:

1. In an electric fuse, a fuse tube, terminals for said fuse tube, the first of said terminals being mounted externally to said fuse tube, a fixed insulating barrier between said first terminal and the interior of the adjacent fuse tube end, a fuse within said tube, electrical connections between said fuse and said terminals, closure means adapted to close to the atmosphere the end of said tube near said first terminal, said closure means being adapted to open under pressure within said tube and thereby to allow the forcible ejection of said fuse material on the blowing of said fuse.

2. In an electric fuse, a fuse tube, terminals for said fuse tube, the first of said terminals being mounted externally to said fuse tube, an insulating barrier between said first terminal and the interior of the adjacent fuse tube end, a fuse within said tube, electrical connections between said fuse and said terminals, closure means adapted to close to the atmosphere the end of said tube near said first terminal said closure means serving as an electrical connection which reverses the direction of the fuse making the circuit from out of the inside of the tube back along the outside of the tube and being adapted to open under pressure within said tube and thereby to allow the forcible ejection of said fuse material and said closure means on the blowing of said fuse.

3. In an electric fuse, a fuse tube, terminals for said fuse tube, the first of said terminals being mounted externally to saidfuse tube, an insulating barrier between said first terminal and the interior of the adjacent fuse tube end, a fuse within said tube, electrical connections between said fuse and said terminals, closure means consisting of a cap which contacts with said first terminal and is adapted to close to the atmosphere the end of said tube near said first terminal, an intermediate terminal member for said fuse near said first terminal which intermediate member is adapted to contact with said fuse and said cap and to serve as part of one of said electrical connections, said closure means being adapted to open under pressure within said tube and thereby to allow the forcible ejection of said fuse material on the blowing of said fuse.

4. In an electric fuse, a fuse tube, terminals for said fuse tube the first of said terminals being mounted externally to 4said fuse tube, an insulating barrier between said first terminal and the interior of the adjacent fuse tube end, a fuse within said tube, electrical connections between said fuse and said terminals, closure means consisting of a cap which contacts with said first terminal and is adapted to close to the atmosphere the end of said tube near said first terminal, an intermediate terminal member for said fuse near said first terminal which intermediate` member is adapted to contact with said fuse and to contact frictionally with said capA when said cap engages said first terminal and adjacent to said first terminal and extending backward along said fuse tube to said first terminal, closure means adapted to close to the atmosphere the end of said tube near Said first terminal, said closure means being adapted to open under pressure and thereby to allow the forcible ejection of said fuse material and said electrical connection on the blowing of said fuse.

In Witness whereof, I aix my signature.

AUGUSTUS JESSE BOWIE. 

